Question

I’m having an issue with some javascript where I am calculating a percentage. It always comes in 1% off:

pcOff = parseInt((1-(PriceFrom/PriceFromRRP))*100);

PriceFrom and PriceFromRRP are captured from a JSON return and in the case of PriceFrom = '40.00' and PriceFromRRP = '50.00' pcOff is being set to 19; it should be of 20. Something funny is going on here. Can anyone shed some light?

Answer 1

(1-(PriceFrom/PriceFromRRP))*100

gives:

19.999999999999996

When you parseInt that, the parser reads digits until it hits a non-digit – i.e. the 19

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Your best bet (for this example) would be to divide last:

100 - PriceFrom*100/PriceFromRRP

20

This prevents the floating point error appearing in the first place